Castors

ABSTRACT

A castor for attachment to a leg or base of an article of furniture comprising a hollow shell of synthetic plastics material open at the bottom to receive a roller and having two spaced side walls. A shaft is mounted across the side walls of the shell, the shaft having grooved ends which are located in Tsection sockets formed in the inner surfaces of the side walls of the shell so as to be hidden from view and so as to support and retain the side walls of the shell against both compressive and bursting forces. A free running roller is mounted on the shaft and vertical support means are provided on the shell, offset laterally from the shaft for mounting the shell pivotally on a supporting member.

United States Patent [191 Daniels CASTORS [75] Inventor: Raymond RobertJames Daniels,

Kings Lynn, England [73] Assignee: Guy Raymond Engineering CompanyLimited, King's Lynn. Norfollg, Ergland [22] Filed: Dec. 29, 1972 [2]]Appl. No.: 319,497

30 Foreign Application Priority Data Jan. 7, 1972 Great Britain 889/72[52] US. Cl. 16/18 A, 16/31 R, 16/48 [51] Int. Cl. B60b 33/00, A47b89/00 [58] Field of Search 16/22, 23, 25, 30, 31, 16/40, 18, 18 A, 20,27, 29, '37, 38, 43, 45-48, 91, 97, 98, 106, 107, 18 R [56] ReferencesCited UNITED STATES PATENTS 19,369 2/1858 Kinzer 16/18 R 300,782 6/1884Koch 16/45 409,495 8/1889 Pederson 16/18 R 556,978 3/1896 Hetzel 16/482,170,257 8/1939 Andersen l6/3l R 1 June 25, 1974 3,210,795 10/1965Fontana et al 16/43 3,343,204 9/1967 Ford 3,345,675 10/1967 Haydock16/45 3,451,095 6/1969 Kiefer 16/107 3,537,125 11/1970 Arenson 16/31 R3,713,186 l/l973 Cartwright l6/45 FOREIGN PATENTS OR APPLICATIONS1,007.210 10/1965 Great Britain 16/18 A Primary Examiner-Donald A.Griffin ABSTRACT pressive and bursting forces. A free running rollerismounted on the shaft and vertical support means are provided on theshell, offset laterally from the shaft for mounting the shell pivotallyon a supporting member.

4 Claims, 8 Drawing Figures PATENTED JUNZ 51374 SHEET 1 OF 2 PATENTEBJUNZ 51874 SHEET 2 OF 2 1 cAsToRs BACKGROUND TO THE INVENTION Thepresent invention relates to a castor for attachment to the leg or baseof an article of furniture.

In the design and manufacture of castors for fumiture, it is necessaryto ensure that the castor has sufficient strength to take the weight ofthe article of fumiture, that it can roll easily in any direction andthat it has a bearing surface which minimises damage to the floorsurface on which the castor stands and moves. It is also necessary toensure that the castor can be economically manufactured and has apleasing appearance.

A conventional castor comprises a roller mounted on a horizontal shaft,the ends of which are journalled in a rigid housing or shell which isitself pivotally mounted on a vertical shaft which is offset from theroller shaft so that the shell and roller can rotate about a verticalaxis and the roller can rotate about a horizontal axis. The shell ofthis type of castor has been formed from a metal or metal alloy ratherthan a synthetic plastics material although synthetic plastics materialshave substantial cost and design advantages, because it has not beenpossible hitherto to design a housing having sufficient strength andrigidity from a synthetic plastics material.

It is therefore an object of the present invention to provide a castorhaving a moulded synthetic plastics shell which has sufficientstructural strength and rigidity to withstand the stresses to which acastor is subjected in'normal use.

It is a further object of the present invention to provide a castor inwhich the ends of the roller shaft are hidden from view and which thushas a pleasing external appearance.

STATEMENT OF THE INVENTION The castor of the present invention comprisesa hollow shell of synthetic plastics material open at the bottom toreceive a roller and having two spaced side -walls, a shaft mountedacross the side walls of the shell so as to support the side walls ofthe shell against compressive and bursting forces, a free running rollermounted on the shaft and vertical support means on the shell offsetlaterally from the shaft for mounting the shell pivotally on asupporting member.

Preferably the internal face of each side wall is formed with aT-section socket, the shaft is formed with a groove adjacent each end ofthe shaft and the ends of the shaft are slidably engaged in the slots,so as to be contained wholly within the castor.

The roller can be formed from any suitable material but is preferablymoulded from a synthetic plastic such as nylon and may comprise twosimilar portions which are independently rotatable.

DESCRIPTION OF THE DRAWINGS roller removed;

FIG. is a section taken on the line V-V of FIG. 3;

FIG. 7 is a view of a detail of the roller of FIGS. 1 to 6 on anenlarged scale; and

FIG. 8 is a section similar to FIG. 6'but taken through a modifiedcastor.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings a castor isindicated generally at 10 which comprises a hollow shell 11, a shaft 12mounted I in the shell 1 l and a roller 13 which is mounted for freerotation on the shaft 12. 1

The shell is formed as an injection moulding from a synthetic plasticsmaterial such as nylon or ABS and is hollow so as to form a cavity toaccept the roller 13. The shell 11 is formed with two side walls 14 and15 respectively, two end walls 16 and 17 respectively and an upper wall18. The side walls and the end walls are outwardly slightly convex inshape to give a pleasing appearance to the shell and the upper wall 18slopes downwardly towards the front end wall 17.

A boss 19 projects upwardly from the upper wall 18 adjacent the rear endwall 16 and the boss 19 is formed with support means comprising a bore20 adapted to receive a spigot.

The side walls 14 and 15 of the shell 11 are formed with upwardlyextending thickened portions 21 and 22 respectively on their insidefaces and slots or sockets 23 and 24 are formed in the thickenedportions 21 and 22 respectively. Each socket 23 and 24 is T-shaped incross-section and extends a short distance upwardly from the bottom edgeof the respective side walls.

The shaft 12 is formed with grooves 25 and 26 respectively adjacent itsends and the dimensions of the T-section sockets 23 and 24 are such thatthe grooved ends of the shaft 12 are a press fit into the sockets 23 and24, as shown in FIG. 4. Two convex shaft retaining cam faces, 27 and 28,are formed on the facing side walls of each socket 23 and 24 a shortdistance from the bottom of the slot to assist in retaining the shaft I2in position at the ends of the slots. The shaft retaining cam faces areshown in FIG. 7. The shaft 12 is a tight friction fit in the sockets 23and 24 and serves as a reinforcement for the shell 11, tying the sidewalls 14 and 15 together and substantially increasing the resistance ofthe shell to both compressive and bursting forces. It will also be notedthat the shaft 12 is contained wholly within the shell 11 and the endsof the shaft are hidden.

The roller 13 is mounted on the shaft 12 as a slide fit before the shaft12 is mounted in the sockets 23 and 24 of the shell 11 and as can beseen from FIG. 6 the roller 13 comprises two similar portions 29 and 30.Each portion 29 and 30 of the roller comprises a smooth annular outerface 31 and 32 respectively, a flat end wall 33 and 34 respectively, acentral tubular portion 35 and 36 respectively, which is mounted on theshaft 12, and a plurality of internal stiffening spokes 37 and 38respectively.

The upper wall 18 of the shell 11 is also formed on its inside face witha plurality of ribs 40 which extend partly down the side walls and endwalls and which stiffen and strengthen the shell further.

The bore 20 in the boss 19 is adapted to receive a pin 41, which isshown in FIG. 5, and which comprises a spigot 42 and'a bearing flange43. The spigot 42 is a FIG. 6 is a section taken on the line VI-VI ofFIG.

push fit into the bore 20 and the bore and spigot are formed with aninterengaging rib 44 and groove 45 respectively which hold the spigot inplace. The pin 41 serves as a means for mounting the castor 10 on theend of the leg of an article of furniture and the castor 10 is freelyrotatable about the spigot 42 when the spigot is located in the borev20.

It will be appreciated that any suitable type of fitting for mountingthe castor on an article of furniture can be provided with a spigot forinsertion in the bore 20 and the type of mounting shown in FIG. does notform a part of the present invention.

In an alternative form of the invention, a metal spigot can bepermanently and non-rotatably moulded or bonded into the boss 19 so asto have a portion projecting upwardly from the boss. The upwardlyprojecting portion of the fixed spigot can then be inserted into afitting on the end of a furniture leg to secure the castor rotatably tothe leg.

As can be seen from FIG. 6 the end faces 33 and 34 of the two portions29'and 30 of the roller 13 are a close fit between the inner faces ofthe enlarged portions 21 and 22 of the side walls 14 and so that thereis very little play between the roller 13 and the sidev walls 14 and 15.The two portions 29 and 30 of the roller 13 are thus held closelytogether although free to rotate in opposite senses orv together asrequired and any tendancy for dust or dirt to get into the roller oronto the shaft I2 is eliminated or at least substantially reduced. Theclose fit between'the shaft and the roller and between the end faces ofthe roller and the inside faces of the shell also substantially reducethe risk of hairs or similar strands from becoming wrapped around theends of the shaft and interfering with the running of the roller.

- The roller is preferably formed from nylon or a material similar tothat from which the shell is made and can either be moulded in twoportions as shown in FIG. 1

to 8 or as a unitary member as shown in FIG. 8.

In FIG. 8 a castor is indicated generally at 50 which is similar to thefastener 10 of FIGS. 1 to 7 except in so far as it includes a unitaryroller 51 mounted in a shell 52 which is substantially narrower than theshell 11 of the castor 10 to accommodate the unitary roller 51.

The unitary roller 51 can optionally be formed with an integral mouldedouter surface 53 as shown in the lower half of the Figure, oralternatively it can be provided with an outer covering 54 as shown inthe upper portion of the Figlire, the outer covering 54 being formedfrom a synthetic rubber material or foam polyurethane which is softerthan the remainder of the roller and which is moulded in place onto theoutside sur- Further minor modifications can be made to the abovedescribed embodiment without departing from the spirit and scope of theinvention which is best described in the following claims.

What I claim is:

l. A castor comprising a hollow, unitary shell of synthetic plasticsmaterial open at the bottom and having two generally parallel laterallyspaced side walls, an inner surface on each side wall formed with avertical socket substantially T-shaped in cross section extendingupwardly from the open bottom of the shell, integral restriction meansspaced from the bottom of each socket, a shaft extending across saidside walls provided with an annular groove adjacent each end forming endportions to fit saidv sockets between said restriction means and thesocket bottom whereby movement of said shaft along said sockets isresisted by said restriction means so as to retain said shaft inposition, said shaft positively'tying the side walls of the shelltogether and supporting same against compressive and twisting forces, afree running roller on said shaft, and vertical support means on saidshell laterally offset from the axis thereof for mounting the shellpivotally on a supporting member.

2. A castor as claimed in claim 1, wherein said integral restrictionmeans comprises cam faces in said socket walls.

3. A castor as claimed in claim 1, wherein said roller comprises twosimilar, unitary portions of synthetic plastics material independentlyrotatable on said shaft and completely filling the width and depth ofsaid shell, said portions having flat closely arranged inner faces insliding engagement with each other for militating against ingress offoreign matter therebetween, and exterior annular surfaces on saidportions cooperatingly shaped to provide a convex rolling surface.

4. A castor as claimed in claim 3, wherein each roller portion comprisesa flat outer wall and flat side walls on said shell arranged in closeparallel juxtaposition to said flat outer walls respectively to minimizethe entrance of foreign matter therebetween.

1. A castor comprising a hollow, unitary shell of synthetic plasticsmaterial open at the bottom and having two generally parallel laterallyspaced side walls, an inner surface on each side wall formed with avertical socket substantially T-shaped in cross section extendingupwardly from the open bottom of the shell, integral restriction meansspaced from the bottom of each socket, a shaft extending across saidside walls provided with an annular groove adjacent each end forming endportions to fit said sockets between said restriction means and thesocket bottom whereby movement of said shaft along said sockets isresisted by said restriction means so As to retain said shaft inposition, said shaft positively tying the side walls of the shelltogether and supporting same against compressive and twisting forces, afree running roller on said shaft, and vertical support means on saidshell laterally offset from the axis thereof for mounting the shellpivotally on a supporting member.
 2. A castor as claimed in claim 1,wherein said integral restriction means comprises cam faces in saidsocket walls.
 3. A castor as claimed in claim 1, wherein said rollercomprises two similar, unitary portions of synthetic plastics materialindependently rotatable on said shaft and completely filling the widthand depth of said shell, said portions having flat closely arrangedinner faces in sliding engagement with each other for militating againstingress of foreign matter therebetween, and exterior annular surfaces onsaid portions cooperatingly shaped to provide a convex rolling surface.4. A castor as claimed in claim 3, wherein each roller portion comprisesa flat outer wall and flat side walls on said shell arranged in closeparallel juxtaposition to said flat outer walls respectively to minimizethe entrance of foreign matter therebetween.